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| United States Patent |
5,160,652
|
|
Small, Jr.
, et al.
|
*
November 3, 1992
|
Dialkylamine complexes of borated higher carbon number alkyl catechols
and lubricating oil compositions containing the same
Abstract
Lubricating oils containing a borated alkyl catechol-dialkylamine complex
are effective in reducing oxidation, wear and deposits in an internal
combustion engine.
| Inventors:
|
Small, Jr.; Vernon R. (Rodeo, CA);
Liston; Thomas V. (San Rafael, CA);
Onopchenko; Anatoli (Concord, CA)
|
| Assignee:
|
Chevron Research and Technology Company (San Francisco, CA)
|
| [*] Notice: |
The portion of the term of this patent subsequent to December 4, 2007
has been disclaimed. |
| Appl. No.:
|
669180 |
| Filed:
|
March 14, 1991 |
Foreign Application Priority Data
| Sep 14, 1990[WO] | PCT/US90/05138 |
| Current U.S. Class: |
508/189; 508/200; 558/290; 558/291 |
| Intern'l Class: |
C10M 139/00 |
| Field of Search: |
252/49.6
558/290,291
|
References Cited
U.S. Patent Documents
| 2344393 | Mar., 1944 | Cook et al. | 252/32.
|
| 2497521 | Feb., 1950 | Trautman | 252/49.
|
| 2795548 | Jun., 1957 | Thomas et al. | 252/74.
|
| 2883412 | Apr., 1959 | Lowe | 252/49.
|
| 3065236 | Nov., 1962 | Young et al. | 260/293.
|
| 3133800 | May., 1964 | DeGray et al. | 44/317.
|
| 3361672 | Jan., 1968 | Andress et al. | 252/49.
|
| 3442807 | May., 1969 | Law | 252/49.
|
| 4328113 | May., 1982 | Horodysky et al. | 252/49.
|
| 4611013 | Sep., 1986 | Ashida | 558/290.
|
| 4629577 | Dec., 1986 | Liston | 252/32.
|
| 4629578 | Dec., 1986 | Liston | 252/49.
|
| 4632771 | Dec., 1986 | Liston et al. | 252/32.
|
| 4643838 | Feb., 1987 | Liston et al. | 252/49.
|
| 4781850 | Nov., 1988 | Doner et al. | 252/49.
|
| 4927553 | May., 1990 | Wright et al. | 252/49.
|
| 4975211 | Dec., 1990 | Small, Jr. et al. | 252/49.
|
| 5061390 | Oct., 1991 | Small, Jr. et al. | 252/49.
|
Primary Examiner: Johnson; Jerry
Attorney, Agent or Firm: Gaffney; R. C., Hagenah; J. A.
Parent Case Text
CROSS-REFERENCES TO RELATED APPLICATIONS
This application is a continuation-in-part of U.S. Ser. No. 407,833, filed
Sep. 15, 1989 now abandoned.
Claims
What is claimed is:
1. A composition comprising a complex of a borated alkyl catechol and an
amount to hydrolytically stabilize the borated alkyl catechol of one or
more secondary amines having the formula:
##STR10##
where R' is phenyl or an aliphatic hydrocarbon radical having from 2 to 9
carbon atoms; and R'' is selected from the group consisting of hydrogen,
phenyl, and an aliphatic hydrocarbon radical having from 1 to 9 carbon
atoms and wherein said aliphatic carbon atoms of R' or R'' or both can
optionally form a 5- or 6-membered alicyclic ring with the alpha carbon
atom; and wherein the total number of carbon atoms in R' plus R'' is no
more than 16; and wherein said borated alkyl catechol has a molar ratio of
alkyl catechol to boron of 1:1 or 3:2 or mixtures thereof and further
wherein the alkyl group of said borated alkyl catechol contains at least
10 carbon atoms.
2. The composition according to claim 1 wherein said alkyl group of said
borated alkyl catechol contains 32 to 60 carbon atoms.
3. The composition according to claim 2 wherein said alkyl group of said
borated alkyl catechol contains 36 to 50 carbon atoms.
4. The composition according to claim 1 wherein said borated alkyl catechol
is a mixture of borated alkyl catechols having alkyl groups of different
carbon number and further wherein said alkyl groups have a number average
carbon number of 35 to 45.
5. The composition according to claim 1 wherein the amount of secondary
amine is at least about 0.8 moles of secondary amine per mole of boron.
6. The composition according to claim 5 wherein the molar ratio of
secondary amine to boron is about 0.8:1 to about 1.1:1.
7. The composition according to claim 1 wherein said borated alkyl catechol
consists essentially of borated alkyl catechol having an alkyl catechol to
boron mole ratio of 3:2.
8. The composition according to claim 7 wherein the molar ratio of
secondary amine to boron is about 1:1.
9. The composition according to claim 1 wherein the borated alkyl catechol
has from one to two alkyl groups and each alkyl group has from 32 to 60
carbon atoms.
10. The composition according to claim 1 wherein the secondary amine is
selected from the group consisting of dihexylamine; dicyclohexylamine; and
ethylbenzylamine.
11. A product prepared by the process which comprises:
(a) forming a borated alkyl catechol wherein said borated alkyl catechol
has a molar ratio of alkyl catechol to boron of 1:1 or 3:2 or mixtures
thereof and further wherein said alkyl group of said borated alkyl
catechol contains at least 10 carbon atoms; and
(b) contacting said borated alkyl catechol with one or more secondary
amines having the formula:
##STR11##
where R' is phenyl or an aliphatic hydrocarbon radical having from 2 to 9
carbon atoms; and R'' is selected from the group consisting of hydrogen,
phenyl, and an aliphatic hydrocarbon radical having from 1 to 9 carbon
atoms and wherein said aliphatic carbon atoms of R' or R'' or both can
optionally form a 5- or 6-membered alicyclic ring with the alpha carbon
atom; and wherein the total number of carbon atoms in R' plus R'' is no
more than 16; under conditions wherein a complex is formed between the
secondary amine and the borated alkyl catechol, the amount of said
secondary amine being sufficient to stabilize said borated alkyl catechol
against hydrolysis.
12. The product prepared by the process according to claim 11 wherein said
alkyl group of said borated alkyl catechol contains 32 to 60 carbon atoms.
13. The product prepared by the process according to claim 11 wherein said
borated alkyl catechol is a mixture of borated alkyl catechols having
alkyl groups of different carbon number and further wherein said alkyl
groups have a number average carbon number of 35 to 45.
14. A method to hydrolytically stabilize a borated alkyl catechol which
comprises contacting said borated alkyl catechol with a hydrolytically
stabilizing amount of one or more secondary amines having the formula:
##STR12##
where R' is phenyl or an aliphatic hydrocarbon radical having from 2 to 9
carbon atoms; and R'' is selected from the group consisting of hydrogen,
phenyl, and an aliphatic hydrocarbon radical having from 1 to 9 carbon
atoms and wherein said aliphatic carbon atoms of R' or R'' or both can
optionally form a 5- or 6-membered alicyclic ring with the alpha carbon
atom; and wherein the total number of carbon atoms in R' plus R'' is no
more than 16; under conditions wherein a complex is formed between said
secondary amine and said borated alkyl catechol; wherein said borated
alkyl catechol has a molar ratio of alkyl catechol to boron of 1:1 or 3:2
or mixtures thereof and further wherein said alkyl group of said borated
alkyl catechol contains at least 10 carbon atoms.
15. The method according to claim 14 wherein the molar ratio of secondary
amine to boron is about 0.8:1 to about 1.1:1.
16. The method according to claim 15 wherein said alkyl group of said
borated alkyl catechol contains 32 to 60 carbon atoms.
17. The method according to claim 15 wherein said borated alkyl catechol
consists essentially of borated alkyl catechol having an alkyl catechol to
boron mole ration of 3:2.
18. The method according to claim 15 wherein said borated alkyl catechol is
a mixture of borated alkyl catechols having alkyl groups of different
carbon number and further wherein said alkyl groups have a number average
carbon number of 35 to 45.
19. The method according to claim 14 wherein said complex is formed in the
presence of a solvent and at a temperature of about 30.degree. C. to about
100.degree. C.
20. A lubricating oil composition comprising a major amount of an oil of
lubricating viscosity and a minor amount of a hydrolytically stable
borated alkyl catechol-secondary amine complex wherein the borated alkyl
catechol of said complex has an alkyl catechol to boron mole ratio of 1:1
or 3:2 or mixtures thereof and further wherein the alkyl group of said
borated alkyl catechol contains at least 10 carbon atoms; and wherein the
secondary amine of said complex has the formula:
##STR13##
where R' is phenyl or an aliphatic hydrocarbon radical having from 2 to 9
carbon atoms; and R'' is selected from the group consisting of hydrogen,
phenyl, and an aliphatic hydrocarbon radical having from 1 to 9 carbon
atoms and wherein said aliphatic carbon atoms of R' or R'' or both can
optionally form a 5- or 6-membered alicyclic ring with the alpha carbon
atom; and wherein the total number of carbon atoms in R' plus R'' is no
more than 16.
21. The lubricating oil composition according to claim 20 wherein the
amount of said complex is from 0.05% to 20% by weight of said composition.
22. The lubricating oil composition according to claim 21 wherein said
borated alkyl catechol is a mixture of borated alkyl catechols having
alkyl groups of different carbon number and further wherein said alkyl
groups have a number average carbon number of 35 to 45.
23. The lubricating oil composition according to claim 21 wherein the
secondary amine is selected from the group consisting of dihexylamine;
dicyclohexylamine; and ethylbenzylamine.
24. The lubricating oil composition according to claim 21 wherein said
alkyl group of said borated alkyl catechol contains 32 to 60 carbon atoms.
25. The lubricating oil composition according to claim 22 wherein said
alkyl group of said borated alkyl catechol contains 36 to 50 carbon atoms.
26. The lubricating oil composition according to claim 21 wherein the
amount of secondary amine is at least about 0.8 moles of secondary amine
per mole of boron.
27. The lubricating oil composition according to claim 26 wherein the molar
ratio of secondary amine to boron is about 0.8:1 to about 1.1:1.
28. The lubricating oil composition according to claim 27 wherein said
borated alkyl catechol consists essentially of borated alkyl catechol
having an alkyl catechol to boron mole ratio of 3:2.
29. A method for reducing oxidation and deposits during operation of an
internal combustion engine comprising operating said internal combustion
engine with a lubricating oil composition according to claim 20.
30. A lubricating oil concentrate comprising a neutral carrier oil and from
about 5 to about 80 weight percent of a hydrolytically stable borated
alkyl catechol-secondary amine complex wherein the borated alkyl catechol
of said complex has an alkyl catechol to boron mole ratio of 1:1 or 3:2 or
mixtures thereof and further wherein the alkyl group of said borated alkyl
catechol contains at least 10 carbon atoms; and wherein the secondary
amine of said complex has the formula:
##STR14##
where R' is phenyl or an aliphatic hydrocarbon radical having form 2 to 9
carbon atoms; and R'' is selected from the group consisting of hydrogen,
phenyl, and an aliphatic hydrocarbon radical having from 1 to 9 carbon
atoms and wherein said aliphatic carbon atoms of R' or R'' or both can
optionally form a 5- or 6-membered alicyclic ring with the alpha carbon
atom; and wherein the total number of carbon atoms in R' plus R'' is no
more than 16.
31. The lubricating oil concentrate according to claim 30 wherein said
alkyl group of said borated alkyl catechol contains 32 to 60 carbon atoms.
32. The lubricating oil concentrate according to claim 30 wherein said
borated alkyl catechol is a mixture of borated alkyl catechols having
alkyl groups of different carbon number and further wherein said alkyl
groups have a number average carbon number of 35 to 45.
33. The lubricating oil concentrate according to claim 30 wherein the molar
ratio of secondary amine to boron is about 0.8:1 to about 1.1:1.
34. The lubricating oil concentrate according to claim 30 wherein said
borated alkyl catechol consists essentially of borated alkyl catechol
having an alkyl catechol to boron mole ratio of 3:2.
35. The lubricating oil concentrate according to claim 30 wherein the
secondary amine is selected from the group consisting of dihexylamine;
dicyclohexylamine; and ethylbenzylamine.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is concerned with the product obtained by reacting a borated
alkyl catechol with certain dialkylamines and the use of said product in
lubricant compositions.
2. State of the Art
Wear and deposits limit the useful life of automobile and truck engines.
Thus, there is a great need to find lubricants that reduce the oxidation,
wear and deposits in the engine, thus increasing the lifetime of the
engine.
U.S. Pat. No. 2,795,548 discloses the use of lubricating oil compositions
containing a borated alkyl catechol The oil compositions are useful in the
crankcase o an internal combustion engine in order to reduce oxidation of
the oil and corrosion of the metal parts of the engine.
There is a problem with the use of borated alkyl catechols in lubricating
oils since they are sensitive to moisture and hydrolyze readily The
hydrolysis leads to haze and/or precipitate formation which must be
filtered out prior to use. It has now been found that the borated alkyl
catechols may be stabilized against hydrolysis by complexing the borated
alkyl catechol with certain dialkylamines.
More importantly, lubricating the crankcase of an internal combustion
engine with a lubricating oil containing the reaction product of a borated
alkyl catechol and certain dialkylamines reduce oxidation and wear in
gasoline engines and deposits in diesel engines.
U.S. Pat. No. 2,497,521 to Trautman relates to the use of amine salts of
boro-diol complexes in hydrocarbon oil compositions. The amine salts of
the boro-diol complexes are useful as stabilizing agents, i.e.,
antioxidants. The described boro-diol complexes include diols selected
from the group consisting of glycols and polyhydroxy benzenes, including
catechol. Catechol is a small polar compound which has poor solubility in
essentially non-polar base oils under ambient conditions. The use of long
chain alkyl groups on the alkyl catechols to enhance its solubility and
compatibility in a base oil is not taught in Trautman. A wide range of
amines to prepare the salts is taught; indeed "any organic amine may be
employed" (Col. 3, lines 51-71).
A recent patent (U.S. Pat. No. 4,328,113) assigned to Mobil Oil Corporation
teaches the use of high molecular weight (C-8+) amines and diamines with
boric acid itself for borated catechols let alone borated alkylated
catechols is not taught in this patent.
U.S. Pat. No. 4,655,948 to Doner et al. discloses grease compositions
having increased dropping points. Among the compositions described are
mixtures of a hydroxy-containing thickener and borated catechol compounds
having the structure:
##STR1##
where R.sub.1 and R.sub.2 are each H or C.sub.1 to C.sub.40 ; and where
R.sub.3 is a C.sub.1 to C.sub.40 hydrocarbyl and can contain,
additionally, oxygen, sulfur and/or nitrogen-containing moieties.
The catechol amine borate compounds of Doner et al., as indicated in the
above formula, are described as trigonal boron compounds having
nitrogen-boron single bonds formed by driving the condensation reaction to
completion via the azeotropic removal of water. A variety of useful amines
are described in Column 2 lines 62, et seq. Although some amines listed
contain secondary amine structures, the common link in all amines is the
presence of primary amine structures. It is also to be noted that Doner's
list of amines are all high molecular weight aliphatic amines, e.g., oleyl
amine or are aromatic, i.e., aniline. Secondary amines, such as
dialkylamine, are not described.
U.S. Pat. Nos. 3,133,800 and 3,203,971 to De Gray et al. disclose glycol
borate amine compounds of aliphatic saturated glycols, useful as fuel
additives, for example as deicing agents and bactericides. Useful amines,
among others, include those with alkyl groups having from 3 to 20 carbon
atoms.
U.S. Pat. No. 2,883,412 to Lowe discloses p-xylylene diamine salts of
glycol boric acids having superior corrosion inhibiting properties. Among
the compounds disclosed are p-xylylene diamine adducts of alkyl catechol
borates, such as derived from butyl and cetyl catechol (Col. 3 lines
61-68).
Reactions of trialkyl borates with amines, including diethylamine,
triethylamine, cyclohexylamine, and ethylenediamine are described by
Wilson in J Chem. Soc. Dalton. 1973, pp. 1628 and by Colclough et al. in
J. Chem. Soc., 1955, pp. 907. The latter, in addition, describes reactions
of triphenylborates with amines and on page 909 shows that attempts to
prepare a diethylamine product resulted in a product that was low in amine
content, but dry ethylamine formed complex with triphenylborate. Moreover,
even the much more stable pyridine complex of triphenylborate described in
this paper hydrolyzed completely in moist air in 5 days. These references
do not mention alkyl catechol derivatives.
However, Kuremel et al. in J. Amer. Chem. Soc. 78, pp. 4572 (1956) does
talk about catechol-boric acid-pyridine complexes. Kuremel shows on page
4574 that "there is complete dissociation of the complexes into their
substituents (pyrocatechol, pyridine, and boric acid) in alcoholic
solution". Alkyl catechols were not mentioned.
U.S. Pat. No. 4,629,578 to T. V. Liston teaches that a complex of borated
alkyl catechol with a succinimide is useful in lubricant compositions. The
succinimide additives of Liston are effective in stabilizing the borated
alkyl catechols to hydrolysis. Preferred succinimides have a number
average molecular weight of about 600 to about 1,500 (Column 4, lines 12,
et seq.). These high molecular weight succinimides effectively dilute the
concentration of the desired borated alkyl catechols. In addition, using
high molecular weight succinimides for hydrolytic stabilization results in
higher transportation costs for the additive, and a loss of flexibility
since their use is limited to formulations containing succinimides as
dispersants, due to compatibility problems.
Previously, it was believed that low molecular weight amines would not be
useful in lubricants subjected to high temperatures, e.g., >100.degree. C.
because of the volatility of the amines; that is, it was believed that the
amines would be lost during use and not provide ongoing stabilization
against hydrolysis. Indeed, all prior art examples show lubricant-type
compositions with higher molecular weight amines than dialkylamines of
this invention.
We have now surprisingly found that certain dialkylamine-borated alkyl
catechol complexes are stable with respect to decomposition to starting
materials under "in use" conditions. The certain dialkylamine stabilized
alkyl borated catechols of this invention passed the L-38 engine test
(with a score of about 30 mg weight loss), where the presence of "free"
amine such as oleyl amine under these conditions would give very high
(300-600 mg) weight losses due to corrosion of the copper and lead
bearings. Also, calorimitry data (DSC) shows that the dialkylamine
stabilized alkyl borated catechols of this invention are stable to about
200.degree. C., which is significantly above the sump temperature of a
gasoline engine.
The thermal stability of catechol boron amine complexes is not predictable.
For example, dimethylamine does not form a stable complex with alkylated
borated catechols nor does diisopropyl amine. The interaction of steric
effects, nitrogen basicity and boron electrophilicity all come into play.
These factors affect the equilibrium between the reactants and the
products and make predictions of thermal stability impossible. One also
cannot predict hydrolytic stability, which may or may not be related to
thermal stability.
The problem, therefore, addressed and solved by this invention is how to
hydrolytically stabilize borated alkyl catechols so as to achieve a higher
concentration of boron per pound of the borated alkyl catechols. This is
achieved by complexing such catechols and stabilizing the same with a low
molecular weight stabilizing material, i.e., certain dialkylamines.
SUMMARY OF THE INVENTION
According to the present invention, lubricating oils are provided which
reduce wear, oxidation and deposits and are especially useful in the
crankcase of internal combustion engines. The reduced wear, oxidation and
deposits result from the addition to the lubricating oil of small amounts
of a complex prepared by reacting a borated alkyl catechol and one or more
dialkylamines having the formula:
##STR2##
where R' is phenyl or an aliphatic hydrocarbon radical having from 2 to 9
carbon atoms and R'' is selected from the group consisting of hydrogen,
phenyl and an aliphatic hydrocarbon radical having from 1 to 9 carbon
atoms and wherein said aliphatic carbon atoms of R' or R'' or both can
optionally form a 5- or 6-membered alicyclic ring with the alpha carbon
atom; and wherein the total number of carbon atoms in R' plus R'' is no
more than 16 (hereinafter defined "dialkylamine(s)").
Preferably, the dialkylamines have from 5 to 15 total carbon atoms, i.e.,
where R' has from 2 to 6 carbon atoms and R'' has from 1 to 7 carbon atoms
and the sum of R' and R''is 3 to 13.
Suitable dialkylamines include ethylpropylamine; dibutylamine;
dihexylamine; dicyclohexylamine, ethylbenzylamine; methylbutylamine;
methylhexylamine; dibenzylamine; and methylcyclohexylamine. The amines can
be used alone or a mixture of amines can be employed.
Unsuitable amines include dimethylamine and diisopropylamine.
The method of preparation of the defined dialkylamines forms no part of
this invention. Such defined dialkylamines are available in the
marketplace or can be prepared by methods known in the art.
Thus, in one aspect, this invention relates to a lubricating oil
composition comprising an oil of lubricating viscosity and a minor amount
of a hydrolytically stable complex of a borated alkyl catechol and the
defined dialkylamines.
In another aspect, this invention relates to a concentrate of a neutral
carrier oil containing from 5 to 80 weight percent (based on the neutral
oil) of the stabilized defined dialkylamine-borated alkyl catechol
complexes of this invention.
These complexes may be readily prepared by contacting (a) a borated alkyl
catechol and (b) a defined dialkylamine under conditions wherein a complex
is formed between the dialkylamine and the borated alkyl catechol, the
amount of the defined dialkylamine being sufficient to stabilize said
borated alkyl catechol against hydrolysis.
Other additives may also be present in the lubricating oils in order to
obtain a proper balance of properties such as dispersancy, corrosion, wear
and oxidation inhibition which are critical for the proper operation of an
internal combustion engine.
In still another aspect of this invention, there is provided a method for
reducing wear, oxidation and deposits in an internal combustion engine by
utilizing the lubricating oil composition described above. Specifically,
improvements in deposits of from 10%-50% may be obtained by employing the
composition of this invention. This deposit improvement can be obtained in
compression-ignition engines, that is, diesel engines. Improvements in
viscosity control of 25%-50% can be obtained in spark-ignition engines,
that is, gasoline engines. That is, lubricating oil compositions
containing the borated alkyl catechol-defined dialkylamine complexes of
this invention have been found additionally to posses (1) antioxidant
properties in gasoline engines and (2) diesel deposit inhibition when
employed in diesel engines.
The borated alkyl catechols may be prepared by borating an alkyl catechol
with boric acid with removal of the water of reaction. Typically, there is
sufficient boron present such that each boron will react with about 2 to 3
hydroxyl groups present in the reaction mixture. (See Formulas IV, V and
VI below.)
The reaction may be carried out at a temperature in the range of 60.degree.
C.-135.degree. C. or higher, in the absence or presence of any suitable
organic solvent which forms an azeotrope with water such as benzene,
xylenes, toluene and the like.
Depending on the ratio of alkyl catechol to boron, the composition of the
borated alkyl catechol, and therefore the composition of the amine adduct
varies. It is believed that at a 3:2 ratio of alkyl catechol to boron and
a 1:1 ratio of boron to nitrogen, the predominant product has a structure
like Formula V below. At a 1:1 ratio of alkyl catechol to boron and a 1:1
ratio of boron to nitrogen the predominant product has a structure like
Formula VI below.
The alkyl catechols or mixtures thereof which may be used to prepare the
borated alkyl catechols used in this invention are preferably mixtures of
monoalkyl and dialkyl catechols. The monoalkyl catechols are preferably of
Formula I
##STR3##
wherein R is alkyl containing at least 10 carbon atoms; usually 10 to
about 60 carbon atoms and preferably from 10 to 30 carbon atoms, more
preferably from 18 to 24 carbon atoms and even more preferably 20 to 24
carbon atoms. Also, up to 60% by weight but preferably less than 40% by
weight of the monoalkyl catechols may have the R group in a position
adjacent or ortho to one of the hydroxy groups and have the Formula II
##STR4##
wherein R is as defined above.
The dialkyl catechols which may be used to prepare a mixture of borated
alkyl catechols of this invention are generally of Formula III
##STR5##
wherein R is as defined above and the two R groups can be the same or
different. Trialkyl catechols may also be employed although they are not
preferred.
As noted above, the alkyl group on the alkyl catechol contains at least 10
carbon atoms. Suitably the alkyl group can have from 10 to 60 carbon atoms
or more and, of course, mixtures of such alkyl groups can be employed.
Among the alkyl catechols which may be employed are decyl catechol, undecyl
catechol, dodecyl catechol, tetradecyl catechol, pentadecyl catechol,
hexadecyl catechol, octadecyl catechol, eicosyl catechol, hexacosyl
catechol, triacontyl catechol, tetracontyl catechol, pentacontyl catechol,
hexacontyl catechol and the like. Also, a mixture of alkyl catechols may
be employed such as a mixture of C.sub.14 -C.sub.18 alkyl catechols, a
mixture of C.sub.18 -C.sub.24 alkyl catechols, a mixture of C.sub.20
-C.sub.24 alkyl catechols, a mixture of C.sub.16 -C.sub.26 alkyl catechols
or a mixture of C.sub.32 -C.sub.60 alkyl catechols.
Higher carbon number alkyl groups, such as those having greater than 30
carbon atoms, are preferably derived from "alpha olefin oligomer(s)." Such
higher carbon number alkyl groups generally contain 32 to 60 carbon atoms,
preferably 36 to 50 carbon atoms.
The term "alpha olefin oligomer" as used herein refers to alpha olefin
dimers, trimers, tetramers and pentamers or mixtures thereof which have
from 32 to 60 carbon atoms. Such alpha olefin oligomers can be prepared or
derived from C.sub.8 to C.sub.20 alpha olefins, preferably C.sub.10 to
C.sub.14 alpha olefins, or mixtures of such alpha olefins. Examples of
alpha olefin oligomers include C.sub.8 tetramers and pentamers; C.sub.10
tetramers and pentamers; C.sub.12 trimers and tetramers; C.sub.14 trimers;
C.sub.16 dimers and trimers; C.sub.18 a dimers; and C.sub.20 dimers. Alpha
olefin oligomers useful in preparing alkyl catechols with higher carbon
number alkyl groups contain preferably 32 to 60 carbon atoms, more
preferably 36 to 50 carbon atoms.
Alpha olefin oligomers can be single carbon number oligomers such as the
tetramer of 1-decene, tetracontene (C.sub.40). Generally, however, the
oligomers used to prepare alkyl catechols having higher carbon number
alkyl groups are mixtures of alpha olefin dimers, trimers, tetramers, and
the like. Such oligomer mixtures can be described by their "number average
carbon number." The "number average carbon number" is determined by
multiplying the number of carbon atoms of each oligomer in the mixture by
the weight percent of that oligomer and then adding the products. For
example, the number average carbon number of an oligomer mixture
containing 10% by weigh C.sub.30, 50% by weigh C.sub.40 and 40% by weight
C.sub.50 is [(30.times.0.10)+(40.times.0.50)+(50.times.0.40)], or 43.
Oligomer mixtures useful in the present invention preferably have a number
average carbon number of about 35 to 45.
The alpha olefin oligomers used herein are prepared by methods well-known
in the art. For example, these oligomers can be prepared using boron
trifluoride catalysts as described in U.S. Pat. Nos. 4,238,343 and
4,045,507, and in Onopchenko, et al, BF3-Catalyzed Oligomerization of
Alkenes (Structure, Mechanisms and Properties), 183rd ACS Natl. Meet. (Las
Vegas, March 1982), Ind. Eng. Chem., Prod. Res. Dev., 22(2), 182-91 (June
1983).
The alkyl catechols of Formulae I, II and III may be prepared by reacting
an olefin having at least 10 carbon atoms, such as a branched olefin or
straight-chain alpha olefin (or mixtures of such olefins) with catechol in
the presence of a sulfonic acid catalyst at a temperature of from about
60.degree. C.-200.degree. C., preferably 125.degree. C.-180.degree. C.,
and most preferably 130.degree. C.-150.degree. C. in an essentially inert
solvent at atmospheric pressure. Although alkylation of catechol can be
carried out neat, in absence of solvents, the use of solvents,
particularly in a batch reactor greatly facilitates the process due to
better contact of the reactants, improved filtration, etc. Examples of the
inert solvents include benzene, toluene, chlorobenzene and Chevron 250
Thinner which is a mixture of aromatics, paraffins and naphthenes.
The term "branched olefin" means that branching occurs at the double bond,
i.e., vinylidene olefins or trisubstituted olefins. The term
"straight-chain alpha olefin" means that the alpha olefin contains little
(less than about 20% or no branching at the double bond or elsewhere.
Monoalkyl catechols are preferred. A product which is predominantly
monoalkyl catechol may be prepared by using molar ratios of reactants
(catechol and alkylating olefin) and preferably a 10% molar excess of
branched olefin or alpha olefin over catechol is used. When used at molar
ratios, the resulting products are generally predominantly monoalkyl
catechols but do contain some amounts of dialkyl catechol. A molar excess
of catechol (e.g. two equivalents of catechol for each equivalent of
olefin) can be used in order to enhance monoalkylation if predominantly
monoalkyl catechol is desired. Predominantly dialkyl catechols may be
prepared by employing a molar excess of olefin, such as two equivalents of
the same or different olefin per equivalent of catechol.
Dialkyl catechols are also useful in this invention. A typical weight ratio
of monoalkyl to dialkyl catechol is in the range of 1:3 to 3:1.
Use of a branched olefin results in a greater proportion of alkyl catechols
of Formula I than use of straight-chain alpha olefins. Use of such
branched olefins generally results in greater than 90% alkyl catechol of
Formula I and less than 10% alkyl catechol of Formula II. On the other
hand, the use of a straight-chain alpha olefin generally results in
approximately 50% of alkyl catechols of Formula I and 50% of Formula II.
In a case of C.sub.20 -C.sub.24 olefin mixture, for example, containing
20% branching, the corresponding alkyl catechols will comprise about 60%
of Formula I and 40% of Formula II. When the same or different olefin
mixture contains 50% branching, the corresponding alkyl catechols will
comprise approximately 70% of Formula I and 30% of Formula II.
The exact structure of the complex of this invention is not known for
certain. However, while not limiting this invention to any theory, it is
believed that the compounds of this invention have a tetrahedral boron
atom with three B-O bonds. The boron is either complexed to the nitrogen
atom in the dialkylamine via dative bonding, or is present as a salt.
##STR6##
wherein R.sub.1 and R.sub.2 can be the same or different and each is
defined the same as R hereinabove. Formula IV illustrates dative bonding.
##STR7##
Formula V is a 3:2 catechol to boron complex.
##STR8##
Formula VI is a 1:1 catechol to boron complex.
A borated alkyl catechol having a 3:2 mole ratio of catechol to boron
(Formula V) or a 1:1 mole ratio of catechol to boron (Formula VI) is a
function of the mole ratio of catechol to boron as noted above. The only
two products that are believed to be present are the 1:1 and 3:2 products
of Formulas V and VI. Nevertheless, due to equilibrium considerations, the
product most likely is a mixture of the 1:1 and 3:2 complexes in varying
proportions depending on the stoichiometry used. We have found that a 3:2
product is just as effective in a Sequence IIID test and the 1:1 product.
It is thus preferred for cost and handling reasons that the borated alkyl
catechol predominate in the 3:2 product and, more preferably, be
substantially only the 3:2 product, i.e., that the product be made using a
mole ratio of alkyl catechol to boron of about 3:2.
The complex may be formed by reacting the borated alkyl catechol and the
defined dialkylamine together neat at a temperature above the melting
point of the mixture of reactants and below the decomposition temperature,
or at a suitable temperature in a diluent in which both reactants are
soluble. Suitable temperatures can be about 30.degree. C. to 100.degree.
C., preferably about 50.degree. C. For example, the reactants may be
combined in the proper ratio in the absence of a solvent to form an
homogeneous product or the reactants may be combined in the proper ratio
in a solvent such as toluene or benzene, xylenes, chlorobenzene, or
thinner, and the solvent then stripped off. The complex formed by either
technique may then be added to the oil. Most defined dialkylamine
complexes of borated alkyl catechols are either liquids at room
temperature, or low melting solids (m.p. 30.degree. C.-40.degree. C.)
depending on the composition of their isomers and the purity of the
product. Alternatively, the complex may be prepared in a lubricating oil
as a concentrate containing from about 5% to 80% by weight of the complex,
which concentrate may be added in appropriate amounts to the lubricating
oil in which it is to be used or the complex may be prepared directly in
the lubricating oil in which it is to be used.
The diluent is preferably inert to the reactants and products formed, and
is used in an amount sufficient to ensure solubility of the reactants and
to enable the mixture to be efficiently stirred.
Temperatures for preparing the complex may be in the range of from
20.degree. C.-200.degree. C. and preferably 25.degree. C.-60.degree. C.
and under sufficient pressure to maintain the defined dialkylamine in the
liquid phase. The most preferred temperatures depend on whether the
complex is prepared neat or in a diluent, i.e., higher temperatures may be
used when a solvent is employed.
An effective amount of defined dialkylamine is added in order to stabilize
the borated alkyl catechols against hydrolysis. In general, mole ratios of
the defined dialkylamine to boron used to form the complex are in the
range of 0.8:1 to 1.1:1, and preferably from 0.9:1 to 1:1, and most
preferably 1:1. This latter ratio is preferred if the complex is made
and/or stored neat or in the absence of solvent or lubricating oil and
under atmospheric conditions. Higher amounts of the defined dialkylamine
can be used but provide no advantages. However, normally excess amine is
added to insure complete stabilization and unreacted amine is recovered
and recycled.
As used herein, the term "stabilized against hydrolysis" means that the
borated alkyl catechol-dialkylamine complex does not "skin-over" or form a
precipitate due to the hydrolysis of the borated catechol for a period of
at least one week, preferably three months, when stored at room
temperature (.apprxeq.15.degree.-25.degree. C.) and ambient humidity,
i.e., no observable or measurable free boric acid is formed. By a
stabilizing amount of amine is meant that amount to stabilize the borated
alkyl catechol against hydrolysis.
The amount of the complex required to be effective for reducing wear,
oxidation and deposits in lubricating oil compositions is a minor amount
and may range from 0.05% to 20% by weight. However, in the preferred
embodiment, it is desirable to add sufficient complex so that the amount
of borated catechol is added at a range from 0.1% to about 4% by weight of
the total lubricant composition and preferably is present in the range
from 0.2% to 2% by weight and most preferably 0.5% to 1%. The dialkylamine
is present in the complex of the invention in an amount effective to
stabilize the borated alkyl catechol against hydrolysis and which allows
the borated alkyl catechol to function as an effective oxidation and
deposit reducing agent.
The defined dialkylamine-borated alkyl catechol complexes of this invention
can be added to a lubricating oil (or can be made in the lubricating oil).
In addition, it is contemplated that the complexes of this invention can
be sold as a concentrate in a neutral oil with or without other
ingredients such as dispersants, antirust agents, etc. The concentrate can
therefore comprise a complex of a borated alkyl catechol and an amount to
hydrolytically stabilize the borated alkyl catechol of dialkylamine plus a
neutral carrier oil. The weight percent of the defined dialkylamine
stabilized borated alkyl catechol in the concentrate is usually from 5 to
80 based on the weight of neutral carrier oil, typically 10 to 60. The
term "neutral oil" is well known in the art, such as those neutral oils
made commercially which have a viscosity in the lubricating oil range,
such as 100 neutral oils, 200 neutral oils, etc.
In general, the complexes of this invention may also be used in combination
with other additive agents in conventional amounts for their known
purpose.
For example, for application in modern crankcase lubricants, the base
composition described above will be formulated with supplementary
additives to provide the necessary stability, detergency, dispersancy,
antiwear and anticorrosion properties.
Thus, as another embodiment of this invention, the lubricating oils which
contain the complexes prepared by reacting the borated alkyl catechols and
the defined dialkylamine may also contain an alkali or alkaline earth
metal hydrocarbyl sulfonate, an alkali or alkaline earth metal phenate,
and Group II metal salt dihydrocarbyl dithiophosphate, and conventional
viscosity index improvers.
The alkali or alkaline earth metal hydrocarbyl sulfonates may be either
petroleum sulfonate, synthetically alkylated aromatic sulfonates, or
aliphatic sulfonates such as those derived form polyisobutylene. One of
the more important functions of the sulfonates is to act as a detergent
and dispersant. These sulfonates are well known in the art. The
hydrocarbyl group must have a sufficient number of carbon atoms to render
the sulfonate molecule oil soluble. Preferably, the hydrocarbyl portion
has at least 20 carbon atoms and may be aromatic or aliphatic, but is
usually alkylaromatic. Most preferred for use are calcium, magnesium or
barium sulfonates which are aromatic in character. Certain sulfonates are
typically prepared by sulfonating a petroleum fraction having aromatic
groups, usually mono- or dialkylbenzene groups, and then forming the metal
salt of the sulfonic acid material. Other feedstocks used for preparing
these sulfonates include synthetically alkylated benzene and aliphatic
hydrocarbons prepared by polymerizing a mono- or diolefin, for example, a
polyisobutenyl group prepared by polymerizing isobutene. The metallic
salts are formed directly or by metathesis using well-known procedures.
The sulfonates may be neutral or overbased having base numbers up to about
400 mg of KOH per gram of sample or more. Carbon dioxide and calcium
hydroxide or oxide are the most commonly used material to produce the
basic or overbased sulfonates. Mixtures of neutral and overbased
sulfonates may be used. The sulfonates are ordinarily used so as to
provide form 0.3% to 10% by weight of the total composition. Preferably,
the neutral sulfonates are present from 0.4% to 5% by weight of the total
composition and the overbased sulfonates are present from 0.3% to 3% by
weight of the total composition.
The phenates for use in this invention are those conventional products
which are the alkali or alkaline earth metal salts of alkylated phenols.
One of the functions of the phenates is to act as a detergent and
dispersant. Among other things, it prevents the deposit of contaminants
formed during high temperature operation of the engine. The phenols may be
mono- or polyalkylated.
The alkyl portion of the alkyl phenate is present to lend oil solubility to
the phenate. The alkyl portion can be obtained from naturally occurring or
synthetic sources. Naturally occurring sources include petroleum
hydrocarbons such as white oil and wax. Being derived from petroleum, the
hydrocarbon moiety is a mixture of different hydrocarbyl groups, the
specific composition of which depends upon the particular oil stock which
was used as a starting material. Suitable synthetic sources include
various commercially available alkenes and alkane derivatives which, when
reacted with the phenol, yield an alkylphenol. Suitable radicals obtained
include butyl, hexyl, octyl, decyl, dodecyl, hexadecyl, eicosyl,
triacontyl, and the like. Other suitable synthetic sources of the alkyl
radical include olefin polymers such as polypropylene, polybutylene,
polyisobutylene and the like.
The alkyl group of the alkyl phenate can be straight-chained or
branched-chained, saturated or unsaturated (if unsaturated, preferably
containing not more than 2 and generally not more than 1 site of olefinic
unsaturation). The alkyl radicals will generally contain from 4 to 30
carbon atoms. Generally, when the phenol is monoalkyl-substituted, the
alkyl radical should contain at least 8 carbon atoms. The phenate may be
sulfurized if desired. It may be either neutral or overbased and if
overbased will have a base number of up to 200 to 300 mg of KOH per gram
of sample or more. Mixtures of neutral and overbased phenates may be used.
The phenates are ordinarily present in the oil to provide from 0.2% to 27%
by weight of the total composition. Preferably, the neutral phenates are
present form 0.2% to 9% by weight of the total composition and the
overbased phenates are present from 0.2% to 13% by weight of the total
composition. Most preferably, the overbased phenates are present from 0.2%
to 5% by weight of the total composition. Preferred metals are calcium,
magnesium, strontium or barium.
The sulfurized alkaline earth metal alkyl phenates are preferred. These
salts are obtained by a variety of processes such as treating the
neutralization product of an alkaline earth metal base and an alkylphenol
with sulfur. Conveniently, the sulfur, in elemental form, is added to the
neutralization product and reacted at elevated temperatures to produce the
sulfurized alkaline earth metal alkyl phenate.
If more alkaline earth metal base were added during the neutralization
reaction than was necessary to neutralize the phenol, a basic sulfurized
alkaline earth metal alkyl phenate is obtained. See, for example, the
process of Walker et al., U.S. Pat. No. 2,680,096. Additional basicity can
be obtained by adding carbon dioxide to the basic sulfurized alkaline
earth metal alkyl phenate. The excess alkaline earth metal base can be
added subsequent to the sulfurization step but is conveniently added at
the same time as the alkaline earth metal base is added to neutralize the
phenol.
Carbon dioxide and calcium hydroxide or oxide are the most commonly used
material to produce the basic or "overbased" phenates. A process wherein
basic sulfurized alkaline earth metal alkylphenates are produced by adding
carbon dioxide is shown in Hanneman, U.S. Pat. No. 3,178,368.
The Group II metal salts of dihydrocarbyl dithiophosphoric acids exhibit
wear, antioxidant and thermal stability properties. Group II metal salts
of phosphorodithioic acids have been described previously. See, for
example, U.S. Pat. No. 3,390,080, Columns 6 and 7, wherein these compounds
and their preparation are described generally. Suitably, the Group II
metal salts of the dihydrocarbyl dithiophosphoric acids useful in the
lubricating oil composition of this invention contain from about 4 to
about 18 carbon atoms in each of the hydrocarbyl radicals and may be the
same or different and may be aromatic, alkyl or cycloalkyl. Preferred
hydrocarbyl groups are alkyl groups containing from 4 to 8 carbon atoms
and are represented by butyl, isobutyl, sec-butyl, hexyl, isohexyl, octyl,
2-ethylhexyl, p-tolyl, xylyl and the like. The metals suitable for forming
these salts include barium, calcium, strontium, zinc and cadmium, of which
zinc is preferred.
Preferably, the Group II metal salt of a dihydrocarbyl dithiophosphoric
acid has the following formula:
##STR9##
wherein R.sub.3 and R.sub.4 each independently represent hydrocarbyl
radicals as described above, and M.sub.1 represents a Group II metal
cation as described above.
The dithiophosphoric salt is present in the lubricating oil compositions of
this invention in an amount effective to inhibit wear and oxidation of the
lubricating oil. The amount ranges from about 0.1% to about 4% by weight
of the total composition, preferably the salt is present in an amount
ranging from about 0.2% to about 2.5% by weight of the total lubricating
oil composition. The final lubricating oil composition will ordinarily
contain 0.025% to 0.25% by weight phosphorus and preferably 0.05% to 0.15%
by weight.
The finished lubricating oil may be single or multigrade. Multigrade
lubricating oils are prepared by adding viscosity index (VU) improvers.
Typical viscosity index improvers are polyalkyl methacrylates, ethylene
propylene copolymers, styrene-diene copolymers and the like. So-called
decorated VI improvers having both viscosity index and dispersant
properties are also suitable for use in the formulations of this
invention.
The lubricating oil used in the compositions of this invention may be
mineral oil or synthetic oils of lubricating viscosity and preferably
suitable for use in the crankcase of an internal combustion engine.
Crankcase lubricating oils ordinarily have a viscosity of about 1300 cSt
at 0.degree. F. to 22.7 cSt at 210.degree. F. (99.degree. C.). The
lubricating oils may be derived from synthetic or natural sources. Mineral
oil for use as the base oil in this invention includes paraffinic,
naphthenic and other oils that are ordinarily used in lubricating oil
compositions. Synthetic oils include both hydrocarbon synthetic iols and
synthetic esters. Useful synthetic hydrocarbon oils include liquid
polymers of alpha olefins having the proper viscosity. Especially useful
are the hydrogenated liquid oligomers of C.sub.6 -C.sub.12 alpha olefins
such as 1-decene trimer. Likewise, alkyl benzenes of proper viscosity,
such as didodecyl benzene, can be used. Useful synthetic esters include
the esters of both monocarboxylic acid and polycarboxylic acids as well as
monohydroxy alkanols and polyols. Typical examples are didodecyl adipate,
pentaerythritol tetracaproate, di-2-ethylhexyl adipate, dilaurylsebacate
and the like. Complex esters prepared from mixtures of mono- and
dicarboxylic acid and mono- and dihydroxy alkanols can also be used.
Blends of hydrocarbon oils with synthetic oils are also useful. For
example, blends of 10 to 25 weight percent hydrogenated 1-decene trimer
with 75 to 90 weight percent 150 SUS (100.degree. F.) mineral oil gives an
excellent lubricating oil base.
Other additives which may be present in the formulation (or in the
concentrate referred to above) include rust inhibitors, foam inhibitors,
corrosion inhibitors, metal deactivators, pour point depressants,
antioxidants, and a variety of other well-known additives.
The following examples are offered to specifically illustrate the
invention. These examples and illustrations are not to be construed in any
way as limiting the scope of the invention.
EXAMPLES
Example 1
Preparation of C.sub.18 -C.sub.24 Alkyl Catechol by Batch Process
A 30-gallon reactor equipped with a stirrer, condenser, Dean-Stark trap,
and nitrogen inlet and outlet, was charged with 61.67 pounds of C.sub.18
-C.sub.24 olefins (less than C.sub.14, 2.7%; C.sub.14, 0.3%; C.sub.16,
1.3%; C.sub.18, 8.0%; C.sub.20, 44.4%; C.sub.22, 29.3%; C.sub.24, 11.2%;
C.sub.26 and above, 2.8%) containing at least 40% branched olefins
(available from Ethyl Corp.), 18.32 pounds catechol, 8.0 pounds sulfonic
acid cation exchange resin (polystyrene cross-linked with divinylbenzene)
catalyst (Amberlyst-15, available from Rohm and Haas, Philadelphia, Pa.),
and 9 gallons of Chevron 350H thinner. With a stirrer set at 150 rpm, the
reaction was carried out at 141.degree. C.-143.degree. C. for a total of
14.7 hours. The reaction mixture was stripped by heating at 143.degree. C.
under vacuum (50 mm Hg) for 4 hours. The product was filtered hot over
diatomaceous earth to afford 67.21 pounds of a liquid C.sub.18 -C.sub.24
alkyl catechol. The product contained 1.4% of unreacted catechol by
infrared analysis, a hydroxyl number of 199 mg KOH/g, and a low sediment
level of 0.01 vol %. Chromatographic analysis showed the product to
contain 2.6% of Chevron 350H thinner, 7.4% unreacted olefin, 45.2%
monoalkyl catechols, and 44.8% dialkyl catechols.
EXAMPLE 2
Boration of C.sub.18 -C.sub.24 Alkyl Catechol
A 3-liter, three-necked, round-bottomed glass flask, equipped with a
stirrer, condenser, Dean-Stark trap, and nitrogen inlet, was charged with
860 g of C.sub.18 -C.sub.24 alkyl catechols prepared according to Example
1, 79.1 g boric acid, and 1200 ml toluene. The reaction mixture was heated
under reflux, while stirring, at 115.degree. C.-125.degree. C., collecting
a total of 50 g of water in the trap in 6 hours. The reaction mixture was
then stripped of solvent by heating at 135.degree. C. under vacuum (20-25
mm Hg) for 3 hours to give 850 g of a liquid, borated C.sub.18 -C.sub.24
alkyl catechol. Analysis for boron gave a value of 1.3%, and a measured
viscosity at 100.degree. C. of 27 cSt. Exposure of a small sample of
product to atmospheric moisture, resulted in boric acid formation on the
surface in a matter of seconds. In less than one day the material was hazy
and crusted on top. This product was prepared using 3 moles of catechol
per 2 moles of boron and the product is believed to have the structure
shown in Formula V above.
Amine Treatment of Borated C.sub.18 -C.sub.24 Alkyl Catechol
A series of runs were made wherein different dialkylamines were complexed
with the borated C.sub.18 -C.sub.24 alkyl catechol prepared according to
Example 2 above.
In each of these runs, which are summarized in Table I below, 10 to 100 g
of the borated C.sub.18 -C.sub.24 alkyl catechol prepared according to
Example 2 above was added to a three-necked, round-bottomed glass flask,
equipped with a stirrer, condenser, and an addition funnel.
While vigorously stirring, an equimolar amount of the corresponding
dialkylamine was added (1 mole N per 1 mole B) to the alkyl catechol over
a period of 1 hour, maintaining a temperature during addition below
50.degree. C. When amine addition was completed, the reaction mixture was
stirred at 50.degree. C. for 1 hour, and then heated to 135.degree. C.
When amine addition was completed, the reaction mixture was stirred at
50.degree. C. for 1 hour, and then heated to 135.degree. C. under vacuum
(20-25 mm Hg) for 1 hour to remove unreacted amine, and any toluene which
may have been added to facilitate mixing and provide a better contact
between the reactants.
TABLE I
______________________________________
Dialkylamine Stabilized Borates
Hydrolytic
Example Borate Stability
Number Amine C:B.sup.1
Rating.sup.2
______________________________________
3 Dihexylamine 3:2 6
4 Dicyclohexylamine
3:2 6
5 Ethylbenzylamine
3:2 6
6 Diisopropylamine
3:2 3
7 Dimethylamine 3:2 1
8 Methylbutylamine
3:2 6
9 Dibenzylamine 3:2 6
______________________________________
.sup.1 Catechol to Boron mole ratio in preparing borate.
.sup.2 1 = Extensive, immediate hydrolysis.
2 = Some immediate hydrolysis.
3 = Hydrolysis within one day.
4 = Hydrolysis within one to three days.
5 = Hydrolysis within three to seven days.
6 = Stable to atmospheric moisture for at least seven days. Examples 3, 4
5, 8 and 9 were stable for more than six months.
Referring to Table I, Examples 3, 4, 5, 8 and 9 used the dialkylamines in
accordance with this invention and were hydrolytically stable for at least
seven days. Examples 6 and b 7 are dialkylamines which do not fit within
the definition of the dialkylamines of this invention and are unsuitable.
Oxidation Bench Tests
A series of oxidation bench tests were carried out which demonstrate the
improvements in antioxidancy of additives prepared according to Examples
3-9.
The oxidation tests were carried out at 171.degree. C. in a glass reactor
and the time required for the sample to consume 1 liter of oxygen was
recorded. The formulation contained 1% of additive to be tested, 3.5% of
dispersant, 50 mmol/kg of sulfonate, 17 mmol/kg of zinc
dialkyldithiophosphates and 6.8% of viscosity index improver in Chevron
100N base oil. The oxidation test was carried out in the presence of metal
catalysts normally found in used oil analysis such as Fe, Cu, Pb, Mn, and
Cr (see U.S. Pat. No. 2,883,412 or U.S. Pat. No. 3,682,980). For
comparison basis, a reference run was carried out under identical
conditions using the same formulation, but containing no additive to be
tested. The results are summarized in Table II.
TABLE II
______________________________________
OXIDATOR B BENCH TEST PERFORMANCE RESULTS
HOURS
EXAM- ADDITIVE OXYGEN IM-
PLE CONC., UPTAKE PROVE-
NUMBER ADDITIVE WT % HR TO 1 L
MENT
______________________________________
10 None -- 12 --
11 Example 1 1.0 13 1
12 Example 2 1.0 22 10
13 Example 2 1.0 23 11
14 Diethylamine
1.0 20 8
Treated
Example 12
15 Diethylamine
1.0 25 13
Treated
Example 13
16 Example 3 1.0 19 7
17 Example 4 1.0 17 5
18 Example 8 1.0 19 7
19 Example 9 1.0 17 5
______________________________________
Referring to Table II, a reference run (Example 10), without an
antioxidant, required about 12 hours to consume 1 liter of oxygen.
Addition of 1% of alkylcatechol of Example 1 (Example 11 in Table II) did
not change the result significantly. This oil in fact failed the Sequence
IIID engine test. When the product of Example 2 was used (Examples 12 and
13 in Table II) both oils showed considerable improvement in oxidation
stability, and both oils passed the Sequence IIID tests. In Example 12,
the additive of Example 2 was used which was prepared from a 3:2 molar
ratio of alkylcatechol to boric acid, while in Example 13, the product was
prepared as in Example 2, but using a 1:1 molar ratio of reactants. It is
evident that boration significantly improved the oxidation stability.
Examples 14 and 15 employed diethylamine stabilized products of Examples
12 and 13. These runs show that the most important ingredient in improving
oxidation stability is incorporation of boron; stabilization with amines,
assuming that a stable complex can be formed, will afford little, if any,
additional benefit to the stability of the base oil. Examples 16 and 17
employed the additives of Examples 3 and 4 and both showed improvement in
oxidation stability, and were therefore expected to pass Sequence IIID
tests. The improvement in stability in Examples 14 and 15, but this is
because higher molecular weight amines were used in Examples 16 and 17
which in effect lowered the boron content of the final blend when compared
to Examples 14 and 15. Therefore, more appropriately, comparison of
additives should be done on the basis of boron content rather than weight
percent of additive. Examples 18 and 19 used methylbutylamine and
dibenzylamine as stabilizing amines. As the data show, both additives
showed improvement in oxidation stability over the reference run (Example
10).
Example 20
Preparation of Alpha-Olefin Oligomer
A sample of unhydrogenated C.sub.30 to C.sub.50 1-decene oligomers was
obtained using procedures essentially the same as those described in U.S.
Pat. No. 4,045,507. The sample had a boiling point above 215.degree. C. at
0.5 mm Hg and contained the following olefins, as determined using
supercritical fluid chromatography: C.sub.30, 14%; C.sub.40, 64%; and
C.sub.50, 22% (number average carbon number C.sub.41). Analysis by NMR for
olefin type showed 95% branched olefins.
Example 21
Alkylation of Catechol with Alpha-Olefin Oligomer Mixture
A mixture of catechol (19.3 grams), the olefin mixture of Example 20 (100
grams), and triflic acid (2 grams) was heated while stirring for 6 hours
at 140.degree. C. The reaction mixture was cooled, taken up in n-hexane
(200 ml) and extracted several times with 100 ml portions of aqueous
2-propanol (75/25) to remove the acid and any unreacted catechol. After
drying over anhydrous sodium sulfate, the product was filtered and then
stripped under high vacuum (about 0.5 mm Hg) at 120-135.degree. C. for 45
minutes to give 111 grams of dark amber alkyl catechol as an oil. This
product gave a hydroxyl number of 105 mg KOH/gram sample, which
corresponds to about 65% yield based on the catechol.
Example 22
Boration of Product from Example 21
The alkyl catechol prepared in Example 21 (105.6 grams) and boric acid (4.1
grams) were reacted by heating, while stirring, at reflux in toluene (100
ml) and collecting the water formed in a Dean-Stark trap. After refluxing
for 3 hours, a total of 3.0 grams of water was recovered, although water
formation stopped after 2 hours. Since no solids were visible, the
reaction mixture was not filtered, and toluene was stripped to give about
106 grams of borated alkyl catechol, which was a fluid at room
temperature. Exposure of a small sample of the purple borated alkyl
catechol to atmospheric moisture led to formation of a boric acid crust on
the surface of the sample, indicating that the boration reaction had
occurred and that the product was hydrolytically unstable. The borated
alkyl catechol was stored under nitrogen for oxidation bench tests and
amine stabilization experiments.
Example 23
Stabilization of Borated Alkyl Catechol from Example 22 with
Diisopropylamine
A mixture of borated alkyl catechol prepared in Example 22 (10 grams) and
diisopropylamine (1.2 grams) in toluene (15 ml) was stirred at room
temperature for 0.5 hours. The reaction mixture was then refluxed at
110.degree. C. for 1 hour and then stripped of solvent by heating to about
135.degree. C. at 0.5 mm Hg for 1 hour to give 10.8 grams of a dark amber,
viscous oil. Exposure of a small sample of product to atmospheric moisture
showed no haze or precipitate formation after standing uncovered in a
petri dish exposed to air for over 30 days.
Oxidation Bench Tests
A series of oxidation bench tests were carried out which demonstrate the
antioxidancy of the additive prepared according to Example 23.
The oxidation tests were conducted using the procedures described in R. W.
Dornte, "Oxidation of White Oils," Industrial and Engineering Chemistry,
28, p. 26 (1936). The formulation contained 2% by weight of the additive
to be tested, 3.5% of dispersant, 50 mmol/kg of calcium as sulfonate, 17
mmol/kg of zinc dialkyl dithiophosphate, and 6.8% of viscosity index
improver in Chevron 100N base oil. The oxidation test was carried out at
171.degree. C. in a glass reactor in the presence of metal catalysts
normally found in used oil (from the Sequence IIIE engine test), such as
Fe, Cu, Pb, Mn, and Cr (added as naphthenates). The time required for the
sample to consume 1 liter of oxygen was recorded For comparison purposes,
a reference run was carried out under identical conditions using the same
formulation, but containing no additive to be tested. The results are
summarized in Table III.
TABLE III
______________________________________
OXIDATOR AO BENCH TEST PERFORMANCE RESULTS
HOURS
EXAM- ADDITIVE OXYGEN IM-
PLE CONC., UPTAKE PROVE-
NUMBER ADDITIVE WT % HR TO 1 L
MENT
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24 None -- 7.8 --
25 Example 22 2.0 27.3 20
26 Example 23 2.0 26.8 19
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Referring to Table III above, a reference run (Example 24), without an
antioxidant additive, required 7.8 hours for the sample to take up one
liter of oxygen. Adding 2 weight percent of the additives of Examples 22
and 23 led to a substantial improvement in the oxidative stability of the
formulated oil blend, demonstrating the effectiveness of additives of this
invention as antioxidants. The slightly better antioxidancy of the
formulated oil blend containing the borated product of Example 22 (Example
25 in Table III) as compared to the formulated oil blends containing the
amine-stabilized product of Example 23 (Example 26 in Table III) may, in
part, be attributed to the dilution effect of the boron level by the
amine.
It is to be understood that various modifications of the present invention
will occur to those skilled in the art upon reading the foregoing
disclosure. It is intended that all such modifications be covered which
reasonably fall within the scope of the appended claims. For example, it
is within the purview of the present invention to use the defined
dialkylamines to stabilize a borated alkyl catechol which has been
partially stabilized with some other stabilizing agent such as a
succinimide or, perhaps, another amine.
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